The growth of the non-wetting liquid 4He on Cs

It was theoretically predicted that the heavy alkali metals provide the only surfaces non-wetted by superfluid 4He below a certain temperature Tw. This was experimentally proven both for Cs and for Rb. However, investigations have shown that the non-wetting thin-film state for the He-Cs system is extremely dilute for T < Tw, yet close to Tw it can be much thicker and of the order of monolayers. Using the photoelectron tunneling method we have sensitively measured the growth of the non-wetting thin-film skate of 4He on a quench-condensed Cs surface. It turns out that far from coexistence there is little adsorption of helium. In contrast, close to GO-existence a rapid growth up to two to three monolayers of helium is observed, but the surface is still non-wet under the usual convention